#include <bits/stdc++.h>
using namespace std;

long long a, b, s, m;

int main() {
	cin >> a >> b >> s;

	for (long long i = 1; i <= a; i++) {
		if (s / i > b) {
			m += (a - i + 1) * (b + 1) * b / 2;
		}
		else {
			m += (a - i + 1) * ((b + 1)* b / 2 - (b - s / i + 1) * (b - s / i) / 2);
		}
	}

	cout << m << endl;
}